1. Field of the Invention
The present invention relates to image formation processing, more specifically, it relates to high rate image formation processing of a gradation expressed by a filled region and one-line image data thereof.
2. Description of the Related Art
There is processing for forming an image from an electronic document and PDL data made up of a plurality of image objects (for example, a character object, an image object, and a graphic object).
An expressing effect where a color or density of an image is changed stepwise is referred to as a gradation.
As a method for expressing a gradation using image objects, there is the one for specifying a plurality of objects with a filled region and a filling color specified.
The method expresses a gradation by causing filled regions to neighbor each other and by changing the filling color thereof stepwise.
The method has a problem in that the number of objects increases and data sizes of an electronic document or PDL data increases.
In order to solve the problem, there is processing for converting object groups expressing a gradation in a vertical or horizontal direction into one-line image data.
On the other hand, it is possible to unify a plurality of filled regions into one filled region (Japanese Patent Laid-Open No. 2003-050683).
By filling the unified filled region while (repeatedly) subjecting one-line image data to expansion processing longitudinally or transversely, expression similar to the gradation expression using a plurality of objects is achieved.
FIG. 1 illustrates an example of forming an image while transversely subjecting one-line image data to expansion processing and to halftone processing.
From one-line image data 101, one pixel of data is obtained by means of expansion processing 102.
The obtained one pixel of data is halftoned by means of halftone processing 103, and written on a memory 104 where an image is formed.
The above-mentioned processing is performed on all pixels in the filled region.
Performing expansion processing and halftone processing as mentioned above on the unified filled region for each pixel will take a very long time for image formation.
In a prior art, it is possible to make data size of an electronic document or PDL data small by expressing a gradation with a filled region and one-line image data thereof, however, as mentioned above, there has been a problem in that it has taken a very long time for image formation.